A couple of years ago, I caught my son (then 5 years old) stealing from me. My husband and I talked to him about it and we thought the matter was resolved, but we recently found out that he has been stealing from one of his playmates. How should we address this?

Can you find out the reason why he did it? Some kids would take things and bring them home because they can't find their own stuff (due to lack of organization they would lose items or can't find them in their place) so they would get na lang what they can see from other kids' tables. Once you know the reason, you can start processing it with the kid about stealing and what it could lead to.